The invention relates to a method of generating an image having a desired brightness, which image is generated by means of a device comprising at least one light source, at least one electro-optical light modulation panel and at least one light-control device, the light from the light source being converted into an image having a desired brightness via at least the electro-optical light modulation panel and the light-control device.
The invention also relates to a device which is suitable for generating an image having a desired brightness by means of such a method, which device comprises at least one light source, at least one electro-optical light modulation panel and at least one light-control device.
In such a method and device known from U.S. Pat. No. 5,597,223, the light-control device comprises a diaphragm having an adjustable aperture. The device is applicable in a light or a dark ambience, with the aperture size being adjusted in dependence upon a light or a dark ambience, such that bright images or images which are rich in contrast are accentuated.
However, the aperture size is not optimized for each image. When, for example, an LCD is used as an electro-optical light modulation panel, the contrast in an image is directly dependent on the desired brightness of this image. When an image to be projected has a relatively low brightness, the LCD is driven accordingly. At a desired, relatively low brightness, the realized contrast is relatively low due to physical properties of the LCD. Consequently, the contrast that can be maximally realized with the LCD cannot be achieved at a desired, relatively low brightness.
It is an object of the invention to provide a method and a device with which a desired brightness and a desired contrast can be realized for each image.
In the method according to the invention, this object is achieved in that the image to be projected is analyzed in a regulator, whereafter the electro-optical light modulation panel and the light-control device are driven, and a too bright image is generated by means of the electro-optical light modulation panel, which image is converted by means of the light-control device into an image having a desired brightness and a desired contrast.
By analyzing preferably each image prior to driving the electro-optical light modulation panel, the light modulation panel can be subsequently driven in such a way that a too bright image having a desired contrast is generated by means of this panel. Simultaneously, the light-control device, which comprises, for example, a diaphragm or a light modulation panel, is driven in such a way that the image generated by means of the light modulation panel and the light-control device has both the desired contrast and the desired brightness.
In the device according to the invention, the object is achieved in that the device comprises a regulator for analyzing the image to be projected, driving the electro-optical light modulation panel for generating a too bright image, and driving the light-control device for converting the too bright image into an image having a desired brightness and a desired contrast.
By driving the light modulation panel as maximally as possible, a maximal brightness and thus a maximal contrast is obtained. The brightness is reduced to the desired level by means of the light-control device.
For an image having large dark areas and large highlights areas, the dark areas can be made perceptually darker by generating a too dark image by the panel, and converting the image into one having the desired brightness and contrast by using the light control device to increase light from the light source.
An embodiment of the device according to the invention is characterized in that the device comprises at least two electro-optical light modulation panels and one light-control device, by means of which images generated on the light modulation panels are simultaneously convertible.
Each light modulation panel is applicable for a different color of the images to be projected. Since each light modulation panel is associated with a light-control device, the light modulation panel can be optimally driven separately for each color by means of the regulator.
These and other aspects of the invention are apparent from and will be elucidated with reference to the embodiments described hereinafter.